The categories shows.

Drivers, features, build quality....

Obviously, all the drivers worked pretty well, and none of the cards fell 
apart in typical use.

>Would you say  there is a difference in sound quality?

On a list that covers the range shown at

http://www.pcavtech.com/soundcards/compare/index.htm

???

#@ll yes, there's a difference in sound quality between the card at the top 
of the list, and the one at the bottom. A huge one.

If so, is that based on  subjective evaluation or specs?

Both. At the top of the list, the cards can only be reliably differentiated 
by technical performance. At the bottom of the list, if you can't hear the 
differences, you don't belong in the audio business. Seriously. The game 
starts shifting above the approximate upper 1/3 of the list.

Detailed listening test studies of several of the cards are provided at

http://www.pcabx.com/product/soundcard/index.htm , and linked out of the 
relevant technical test reports.